An ultrasonic diagnostic apparatus is a diagnostic apparatus for displaying an image of information on the inside of a living body, and is inexpensive and requires no exposure to radiation as compared with other image diagnostic apparatuses such as an X-ray diagnostic apparatus and a computerized transverse axial tomography. Thus, the ultrasonic diagnostic apparatus is used as an apparatus useful for noninvasive real-time observations. The ultrasonic diagnostic apparatus is widely applied to the diagnoses of circulatory organs such as a heart, abdominal organs such as a liver and a kidney, peripheral blood vessels, gynecology, and breast cancer.
In general, the ultrasonic diagnostic apparatus transmits convergent ultrasonic waves (transmission beam) for one scan line one time, and receives signals focused in the transmission direction, thereby acquiring diagnostic information (ultrasonic image data) regarding parts on the scan line. Further, the ultrasonic diagnostic apparatus sequentially changes the scanning direction to repeatedly transmit and receive ultrasonic waves for the individual scan lines in a similar manner, thereby finally generating two-dimensional or three-dimensional diagnostic images. In recent years, a method (simultaneous reception) that obtains diagnostic information regarding parts on more than one scan line in one transmission has also been used. This method transmits convergent ultrasonic waves, and provides echo signals thus obtained with different reception delays to add delays in parallel more than once, thereby creating reception beams corresponding to more than one direction. In general, if a reception focus is set on the transmission direction, a highest quality diagnostic image can be obtained.
Meanwhile, the convergent ultrasonic waves used in transmission always have a focus. This focus is generally represented by a mark, on an image so that an operator can recognize the position and size of the focus. In general, spatial resolution is highest in the vicinity of the focus. Therefore, the operator changes and sets, for example, a focal position on an image in accordance with the position and size of a region of interest. The ultrasonic diagnostic apparatus changes a transmission delay pattern in accordance with, for example, the position of a set focus mark to change an actual transmission focus.
The position and shape of the transmission/reception focus influence the spatial resolution. Thus, for an examiner, details of the transmission/reception focuses are important information that influences the image quality. For example, regarding a first sound field (beam profile) from the left in FIG. 12 formed by a transmitted pulse, the degrees of in-focus or out-of-focus convergence can be visually recognized. Here, border lines 81 are contour lines of sound pressure in the sound field, and an echo signal inside the border lines 81 can be considered to be the main component of a diagnostic image. The first beam profile from the left in FIG. 12 and the second beam profile from the left in FIG. 12 have the same focal position. However, the aperture at the focus is narrower and the spatial resolution in this place is higher in the first beam profile from the left in FIG. 12 than in the second beam profile from the left in FIG. 12. The first sound field from the left in FIG. 12 and the third sound field from the left in FIG. 12 have the same spatial resolution at the focus. On the contrary, it is apparent that the beam profile including out-of-focus parts is narrower in the third sound field from the left in FIG. 12 and that the overall spatial resolution is higher in the third sound field from the left in FIG. 12.
However, the conventional ultrasonic diagnostic apparatus only provides information on the position where the focus is present, so that it is impossible to known, for example, the difference between the first sound field from the left in FIG. 12, the second sound field from the left in FIG. 12, and the third sound field from the left in FIG. 12. That is, according to the conventional ultrasonic diagnostic apparatus, it is impossible to intuitively known how the actual position and shape of the transmission/reception focus influence the image quality.
It has been made in view of such circumstances, and is directed to provide an ultrasonic diagnostic apparatus and an ultrasonic image processing apparatus that generate an image (beam profile image) regarding an actual sound field and enable direct visual recognition of, for example, the shape and focal position of a sound field formed in ultrasonic wave transmission/reception.